1. Field of the Invention
This invention relates to stepladders. More particularly it concerns stepladders made of extruded aluminum metal parts structured so the ladders will be extremely light and of low cost, but still strong and substantially free of torsional twisting, pantographing or relative rotation of parts.
2. Description of the Prior Art
Ladder manufacturers strive to create ladders from a minimum of parts and material to make them as light weight and as low in cost as possible. Stepladders designed with such considerations in mind are disclosed in many prior patents, e.g., U.S. Pat. Nos. 2,899,008 and 3,009,535.
There tends to be a trade-off in ladder construction between strength and stability versus light weight and minimum material of construction. Thus, as the number of parts and weight of material used in fabrication of ladders is decreased, there is an increased tendency for the strength and proper functioning of the ladders to decrease. By way of example, light weight stepladders frequently exhibit unsatisfactory torsional twisting of the rear section relative to the front section during use. Also, pantographing or rotation often occurs in the rear sections of light weight ladders. Moreover, proper bracing of the front section and bucket rack support are problems in such ladders.
Not withstanding the large number of new designs of ladders that have been developed over the years, there continues to be a need for the creation of stepladders that possess high strength and stability combined with light weight, low material requirement and low cost of fabrication.